Apparatus for gas purification



K. COX ET AL APPARATUS FOR GAS PURIFICATION Maiy l, 1923.

Filed March 5. 1923 luvslvroies;

I KENNETH Cox ROBERT Pems KEQIZ EFNEST BATY Patented May 1, 1923.

UNITED STATES PATENT OFFICE;

xmmnrn cox, or ru'rnnr, Lennon, ROBERT ralcama, or alumnae-cron- I cum, AND ERNEST JOGELYK nary, OFLU'IOH', momma.

arrmrus ron oas rumncanon.

Application filed lama. a, use. Serial a. 022,084.

Britain, residing, respectively, in Putney,

London, Englandin the county of Luton, in the county of Bedfor En land, have invented certain new and usefu Im- Gateshead-upon-Tyne,

provements in Apparatus for Gas Purification, of which the following is a specification. 0'

This invention relates to apparatus for gas purification, according to which the sulphuretted hydrogen and '(or) sulphur dioxide in the gas is or are removed and sulphur recovered, the gas to be purified being passed throu h a bed of contact material consisting of 0g iron .ore or other oxide of iron or oxide of alumina, manganese and the like, or mixtures of these, the contact material being heated by the reaction and the sulphur compound being decomposed, with the resulting formation of elemental sulphur, which is recovered; and the term contact material as used herein and in the statement of claim hereto is to be understood to refer to any suitable substance such as the'above which will give the desired reaction; and the object of the present invention is to improve the apparatus in which the purification process is carried out, par ticularly in respect to the mode of control ling the temperature of the reaction in the contact material, so that with moderate temperatures and small temperature gradients, a high and uniform efliciency is maintained. According to the invention, this object is accomplished by controlling the temperature of the reaction in the contact material by means of suitable heat exchanging surfaces so disposed in the bed of contact material that on one side the said surfaces are in contact with thesaid material and on.the other side are in contact with an attemperating fluid; the said surfaces being so distributed throughout the bed of contact material-that, whilst the latter is divided into comparatively small sections each subjected to the action of the attemperating fluid, the aggregate cross-sectional area of material, normal to the direction of flow of the gases, is considerable, whereby the transfer ofi heat through the said surfaces either to or from the said material, in conjunction with burham, En land; and

the heat evolved by the maction itself, maintams a uniform temperature of reaction throughout, sufliciently hi h to revent any substantial de sition .0 .sul ur in the contact materia and to ensure the sulphur being carried away from the reaction zone- 1n the eflluent ases, and sufliciently low to maintain it in t evelemental state.

The heat exchanging surfaces may convenlently be plpes arranged in zig-za or coils embedded in the contact materia through the interiorof which pipes the attemperatmg fluid flows, the pipes being distributed throughout thdmaterial so that the latter is divided into comparatively small sections each suhf'ect to the action of the attem ratlng flui and the gases to be treated pass through these-sections in parallel streams; this arrangement is found to give veryv ood results butanygother arrangement of eat transmitting surfaces may be employed which will provide a comparatively lar aggregate sectional area transversely to t e flow of gases.

Steam may conveniently be employed as an attemperating fluid, in which case the heat transmitting surfaces may un'one side he an extension of the steam space of a steam generator to which the condensed water returns; in cases'where the composition of the gases to be treated require it liquids having a boiling point higher than that of water may be employed; or flue gases suitably controlled by a dam er may be arranged to pass through the heat exchanging surfaces.

The heat exchanging surfaces are utilized I at the commencement of the process to heat the oxide and (or) the gas so as to provide at once the temperature necessa to ensure the required degree of purificatlon and to carry off the sulphur with the effluent gas instead of depositing it in the oxide or contact material, thus obviating the necessity for a prolonged passage of heated gas 100 through the apparatus, (without resultant purification) at the'commencement of operations.

The contact material may, as stated, be any of the known materials suitable for the 5 purpose such as oxides of iron, alumina, manganese or the like or mixtures of these.

The object of the invention being to maintain the temperatures of the reaction zone etted hydrogen and its elimination from the the reacting zone as elementalsulphur, it will be understood that if, owing to the evolution of heat by'the reaction or other causes, the temperature tends to rise unduly, e. g

to such a temperature as to cause the recombination of the elemental sulphur, the optium temperature must be maintained by abstracting instead of by adding heat.

Our process is generally applicable for purifying gas containing sulphuretted hydrogen and is particularly suitable for the urificationof gases having a comparatively ow content thereof, say, as low as 0.1 per cent, by volume; in purifying a gas having a low sulphuretted hydrogen content, the heat evolved as a result of the reaction itself is comparatively small, and in order to maintain a steady reaction temperature required according to the invention, it is necessary with such a gas to add continuously, by means of the heat exchanging surfaces, more or less heat as may be required. Where the sulphuretted hydrogen content is such that the heat evolved in the reaction itself is, theoretically, that necessary to maintain the temperature at or about the desired value, the heat exchanging surfaces are subjected to an attemperating fluid of suitable temperature which has a steadying value and compensates for the fluctuations in atmospheric conditions and in the character of as to be purified. Where the sulphuretted hydrogen content is substantially higher than 1 per cent, the temperature of the reaction tends to rise to a value which converts the sulphur into sulphur di-oxide which is undesirable, and in purifying such gases the heat exchanging surfaces are used to extract heat from the zone of reaction.

Where by reason of the low content of sulphuretted hydrogen in the gas, the heat to be added to maintain the desired temperature is considerable, the said heat may be added to the 'gas as it enters the reaction zone by heat exchanging surfaces which may conveniently transfer heat from the outgoing to the incoming gas and the heat exchanging surfaces in contact with the contact material may be used to deal with the transfer of the balance of heat necessary, by reason of variationsfrom time to time in atmospheric conditions or in the sulphur content of the gas, to maintain a steady temperature.

We find that the maintenance of an even steady temperature of reaction very considerably increases the efficiency of the process, the catalytic .value of the contact material being under such circumstances very marked; the effect of this increased efiiciency being to reduce to a minimum the quantity of contact material necessary.

Provision is made, say by extending the masses heat exchanging surfaces into the outlet passage-way from the space in web. the reaction takes place, to ensure that the sulphur will remain in vapourized and (or) suspended condition until it enters the first .con-

densing or collecting apparatus.

The temperature by which the operation is controlled may conveniently be that of the attemperating medium determined as follows z-The efiiuent gases are tested for pur-' ity and when the desired degree of purity is reached, the temperature of the attemperating medium corresponding with this degree is ascertained, and this temperature is then maintained either by hand regulation or by the use of automatic devices such as thermostats or the-like. The temperature of the efiluent gas is usually maintained as low as is consistent with the prevention of any sub-" stantial deposition of sulphur in the oxide.

Thesulphur may Ebe separated from the efiiuent gas by any suitable means, say by passing the gas tangentially into a cyclone apparatus in which the sulphur is separated from the gas by condensation and by centrifugal force, and from which it can be drawn off from time to time.

Where the nature of the gas to be purified requires it, air is usually supplied to the gas as it enters the reaction chamber, so as to provide the oxygen necessary for the re-- action. In selecting a contact material from the range of substances described, the natmre of the gas to be purified will naturally have to be'taken into consideration, and .care is taken to select a contact substance in which there will be a minimum of permanent sulphiding and one which will be immune from so called poisons which affect the efiiciency of the catalytic substances.

We have illustrated, by way of example, an apparatus suitable for carrying out our invention, in the accompanying drawings which are diagrammatic; the precise form of the apparatus and the details of construction being such that those skilled insuch matters would have no difliculty in-installing a plant to meet requirements; in the draw- The container A which may be of any suitable shape is usually constructed of cast iron but any suitable material may be employed; it may be lagged to prevent heat exchanges with the outer atmosphere; the

container is fitted with a cover a and the gas inlet B may be formed on the cover, as shown, or be independent of the latter. C is the outlet for the efiiuent gas.

- At a suitable distance from the bottom of the receiver agrating D is fitted (which for clearness is not shown in the plan) which end E and leaves by the outlet pipe G; the

eflluent'gas outlet C is provided with an annulus or jacket 0 and the attem eratlng medium on its way to the outlet passes through the "said jacket and tends to maintain the desired temperature of the eflluent J is a sulphur collecting chamber and maybe of the well known cyclone type, K being the sulphur discharge valve, and L the purified gas outlet pipe.

Where it-is desired to raise the temperature of the contact bed the temperature of the heating medium may be raised by various methods such as I (a) The supply of live steam from a main boiler at the inlet E of the coil E, and the connection of the outlet G of the coil to a steam trap.

(b) The supply of steam from a small boiler or heated coil for use on the purifying plant alone, the condensedwater flowing back from the outlet G by gravity to the said boiler or heated coil.

(0) The circulation of hot water through the coil either by thermo-syphon action or by positive means. I 1

(d) The circulation of liquids other than water, preferably those having a high boiling point such as certain oils obtained from the low temperature carbonization process.

(e) The supplyto the inlet E of va ur obtained from the boiling of such liqui s as described in (d) the condensate flowing back to the boiler through the outlet G.

The object of using such a liquid or its vapour as in (d) or (e) in preference to water and steam, is that a high temperature may be maintained without a corresponding high pressure.

In some cases we may employ flue gases of suitable temperature from a furnace quite separate from the heat exchanging surfaces and so arranged that the flow of the flue gases through the said surfaces can be efi'ectively regulated; where heat has to be continuously abstracted from the reaction zone, the attemperating fluid may be any suitable liquid or fluid, say water, maintained at the appropriate temperature.

The means illustrated by way of example for supplying and circulating the attemperating fluid, comprise a vertical boiler M fitted. with a superheater coil O, through which coilthe steam generated pass'eson its way to the inlet E of the heat exchanging surfaces E, the outlet G from the and surfaces being connected to the water space the condensation of the steam as it parts of the boiler, so that the ,water formed by with its heat flows back to'the steam generato'r. The desired temperature is maintamed by controlling, by means of a valve such as P, the quantity of fluid supplied,

or by controlling the temperature 0 the said fluld by regulating the a furnace temperature by means of a damper Q, the admission of air above thefire through the air regulator R, or by any other suitable means.

The gas enters the container A, at B, and passes throu h the contact material H- where the desired reaction takes place, and

the outlet gas now containing sulphur in elemental form, passes through the outlet G into the cyclone or other separator J. The sulphur is there separated from the gas partly by condensation and partly by centrifugal action, and may be removed from time to time through the valve K.

' The gas now free from sulphur passes away through the outlet pipe L. Under certain conditions it may be necessary to install a secondor third cyclone in series to extract the last traces of sulphur.

Several unlts such as the one illustrated, may be provided, the gases being passed through them either .in series or in parallel, as may be required.

In the apparatus illustrated by way of example, the heat exchanging surfaces are shown as pipes embedded in the contact material; the same result may be obtained by arranging the heat exchanging surfaces in cellular or honey-comb form, as in radiators for cooling circulating water, the gases to be purified passing in parallel streams through the one set of passageways containing the contact material, and

the attemperating fluid being circulated through spaces bounded by the walls of the said passage-ways, which walls form the heat exchanging surfaces, several cellular units of this type being embedded, if necessary, in the one bed of contact material.

A heat exchanger may be interposed between the incoming and outgoing gases, so that the heat of the latter may be transferred to the former.

For purifying a volume of gas of one million cubic feet per day according to the ordinary methods of gas purification, it would be necessary to employ at least four oxide boxes, each measuring 25 feet square, whereas, according to this invention the same volume of gas can be purified by passage through a single box measuring 6 feet square with a proportlonate reduction of space occupied and cost of erection.

' Having now fully described our invention, we declare that what we claim and desire to secure by Letters Patent is In apparatus for purifying gas by the removal of sulphur compounds and for the recovery of sulphur, the combination of;- a containing vessel having an mlet for the v gas to be treated and an outlet for the treated gas; a bed of contact material arranged across the path of flow of the gas from the inlet to the outlet; hollow heat exchanging surfaces embedded in the said material; means for supplying an attemperating fluid to the interior of the heat exchanging surfaces; means for separating,

KENNETH COX. ROBERT PRICE KERR. ERNEST JOCELYN BATY. .Witnesses:

CHARLEs WEBSTER, Camus PALMER. 

